Large commercial aircraft have many different exterior lights. An exemplary group of exterior aircraft lights are lights for passive visibility, such as navigation lights and anti-collision lights. Another exemplary group of exterior aircraft lights are headlights that allow the pilots to view the area in front of them, when they are seated in the cockpit, such as taxi lights, take-off lights, landing lights, and runway turn-off lights. Yet another example of exterior aircraft lights are scan lights that allow the inspection of the aircraft structure in the dark, such as wing scan lights.
Light units for illuminating the vertical stabilizer at the tail of an aircraft have a number of purposes. First, they allow for an inspection of the vertical stabilizer in the dark, such as during an operational check of the rudder. Second, they allow for providing an indication of the extension of the aircraft in the dark, because the illuminated area is a good estimate of where the tail end of the aircraft is. Third, they help in identifying aircraft during the approach or during taxiing on the air field, because the vertical stabilizer commonly contains an airline logo. For this reason, the vertical stabilizer illumination light units are often also referred to as logo lights.
An exemplary tail of an aircraft 100 is shown in FIG. 1. The aircraft 100 has two horizontal stabilizers, one of them being shown in the viewing direction of FIG. 1 and being indicated with reference numeral 102. Further, the aircraft 100 has a vertical stabilizer 104, mounted to the top of the fuselage of the aircraft 100. The horizontal stabilizer 102 comprises a vertical stabilizer illumination light unit that emits light towards the vertical stabilizer 104 for illuminating the same. In FIG. 1, there is depicted a circle 150 that illustrates an illumination cone representing the area illuminated by a prior art vertical stabilizer illumination light unit. As can be seen from FIG. 1, the illumination cone 150 illuminates a large portion of the vertical stabilizer 104. However, it also emits a large amount of light that passes the vertical stabilizer 104 and is, therefore, not used for the illumination of the vertical stabilizer 104. In other words, such a prior art vertical stabilizer illumination light unit emits a large amount of “wasted” light.
Accordingly, it would be beneficial to provide an aircraft vertical stabilizer illumination light unit that has an improved light usage efficiency.